Method and apparatus for utilizing other sector interference (osi) indication

ABSTRACT

Techniques for mitigating interference in a wireless communication system are described. In one design, a sector may determine multiple fast other sector interference (OSI) indications for multiple subzones, with each subzone corresponding to a different portion of the system bandwidth. At least one report may be generated for the multiple OSI indications, with each report including at least one OSI indication for at least one subzone. Each report may be encoded to obtain code bits, which may then be mapped to a sequence of modulation symbols. A sequence of modulation symbols of zero values may be generated for each report with all OSI indications in the report set to zero to indicate lack of high interference in the corresponding subzones. This allows a report to be transmitted with zero power in a likely scenario. A regular OSI indication may also be determined for the system bandwidth and transmitted.

The present application is a Divisional of U.S. application Ser. No.11/968,638, entitled “METHOD AND APPARATUS FOR UTILIZING OTHER OTHERSECTOR INTERFERENCE (OSI) INDICATION,” filed Jan. 2, 2008, which claimspriority to provisional U.S. Application Ser. No. 60/883,387, entitled“A METHOD AND APPARATUS FOR FAST OTHER SECTOR INTERFERENCE (OSI)ADJUSTMENT,” filed Jan. 4, 2007, and provisional U.S. Application Ser.No. 60/883,758, entitled “WIRELESS COMMUNICATION SYSTEM,” filed Jan. 5,2007, both assigned to the assignee hereof and incorporated herein byreference.

BACKGROUND

I. Field

The present disclosure relates generally to communication, and morespecifically to techniques for mitigating interference in a wirelesscommunication system.

II. Background

Wireless communication systems are widely deployed to provide variouscommunication services such as voice, video, packet data, messaging,broadcast, etc. These wireless systems may be multiple-access systemscapable of supporting multiple users by sharing the available systemresources. Examples of such multiple-access systems include CodeDivision Multiple Access (CDMA) systems, Time Division Multiple Access(TDMA) systems, Frequency Division Multiple Access (FDMA) systems,Orthogonal FDMA (OFDMA) systems, Single-Carrier FDMA (SC-FDMA) systems,etc.

A wireless multiple-access communication system can concurrentlycommunicate with multiple terminals on the forward and reverse links.The forward link (or downlink) refers to the communication link from thebase stations to the terminals, and the reverse link (or uplink) refersto the communication link from the terminals to the base stations.Multiple terminals may simultaneously transmit data on the reverse linkand/or receive data on the forward link. This may be achieved bymultiplexing the transmissions on each link to be orthogonal to oneanother in time, frequency and/or code domain.

On the reverse link, the transmissions from terminals communicating withdifferent base stations are typically not orthogonal to one another.Consequently, each terminal may cause interference to other terminalscommunicating with nearby base stations and may also receiveinterference from these other terminals. The performance of eachterminal may be degraded by the interference from other terminalscommunicating with other base stations.

There is therefore a need in the art for techniques to mitigateinterference in a wireless communication system.

SUMMARY

Techniques for mitigating interference in a wireless communicationsystem are described herein. In an aspect, a sector may estimateinter-sector interference observed by the sector from terminalscommunicating with neighbor sectors. The sector may generate andtransmit other sector interference (OSI) indications that convey theamount of interference observed by the sector. In one design, the OSIindications may include a regular OSI indication and fast OSIindications. The regular OSI indication may be generated based onlong-term average interference, which may be obtained by averaginginterference over a larger frequency range and across a longer timeinterval. The fast OSI indications may be generated based on short-termaverage interference, which may be obtained by averaging interferenceover a smaller frequency range and across a shorter time interval. Aterminal may adjust its transmit power based on the regular and fast OSIindications received from neighbor sectors.

In one design, a sector may determine multiple fast OSI indications formultiple subzones, with each subzone corresponding to a differentportion of the system bandwidth. At least one report may be generatedfor the fast OSI indications, with each report including at least onefast OSI indication for at least one subzone. Each report may be encodedto obtain code bits, which may then be mapped to a sequence ofmodulation symbols. A sequence of modulation symbols of zero values maybe generated for each report with all fast OSI indications in the reportset to zero to indicate lack of high interference in the correspondingsubzones. This allows a report to be transmitted with zero power in alikely scenario. A regular OSI indication may also be determined andtransmitted.

In one design, a terminal may receive at least one fast OSI indicationfor at least one subzone and may determine its transmit power based onthe at least one fast OSI indication. At least one delta may bemaintained for the at least one subzone and may be adjusted based on theat least one fast OSI indication. Transmit power for a reference (e.g.,pilot) channel may be determined based on closed-loop power control. Thetransmit power for each subzone may then be determined based on thedelta for the subzone and the transmit power for the reference channel.

Various aspects and features of the disclosure are described in furtherdetail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communication system.

FIG. 2 shows a superframe structure.

FIG. 3 shows a power control mechanism.

FIG. 4 shows a process for transmitting OSI indications.

FIG. 5 shows an apparatus for transmitting OSI indications.

FIG. 6 shows a process for receiving OSI indications.

FIG. 7 shows an apparatus for receiving OSI indications.

FIG. 8 shows a block diagram of a terminal and two sectors/basestations.

DETAILED DESCRIPTION

FIG. 1 shows a wireless communication system 100, which may also bereferred to as an access network (AN). The terms “system” and “network”are often used interchangeably. System 100 includes multiple basestations 110, 112 and 114 and multiple terminals 120. A base station isa station that communicates with the terminals. A base station may alsobe referred to as an access point, a Node B, an evolved Node B, etc.Each base station provides communication coverage for a particulargeographic area 102. The term “cell” can refer to a base station and/orits coverage area depending on the context in which the term is used. Toimprove system capacity, a base station coverage area may be partitionedinto multiple smaller areas, e.g., three smaller areas 104 a, 104 b and104 c. Each smaller area may be served by a respective base stationsubsystem. The term “sector” can refer to the smallest coverage area ofa base station and/or a base station subsystem serving this coveragearea.

Terminals 120 may be dispersed throughout the system, and each terminalmay be stationary or mobile. A terminal may also be referred to as anaccess terminal (AT), a mobile station, a user equipment, a subscriberunit, a station, etc. A terminal may be a cellular phone, a personaldigital assistant (PDA), a wireless communication device, a wirelessmodem, a handheld device, a laptop computer, a cordless phone, etc. Aterminal may communicate with zero, one, or multiple base stations onthe forward and/or reverse link at any given moment.

For a centralized architecture, a system controller 130 may couple tobase stations 110 and provide coordination and control for these basestations. System controller 130 may be a single network entity or acollection of network entities. For a distributed architecture, the basestations may communicate with one another as needed.

The techniques described herein may be used for a system with sectorizedcells as well as a system with un-sectorized cells. For clarity, thetechniques are described below for a system with sectorized cells. Inthe following description, the terms “sector” and “base station” areused interchangeably, and the terms “terminal” and “user” are also usedinterchangeably. A serving sector is a sector with which a terminalcommunicates. A neighbor sector is a sector with which the terminal isnot in communication.

The techniques described herein may also be used for various wirelesscommunication systems such as CDMA, TDMA, FDMA, OFDMA, and SC-FDMAsystems. A CDMA system may implement a radio technology such ascdma2000, Universal Terrestrial Radio Access (UTRA), etc. An OFDMAsystem may implement a radio technology such as Ultra Mobile Broadband(UMB), Evolved UTRA (E-UTRA), IEEE 802.11, IEEE 802.16, IEEE 802.20,Flash-OFDM®, etc. UTRA and E-UTRA are described in documents from anorganization named “3rd Generation Partnership Project” (3GPP). cdma2000and UMB are described in documents from an organization named “3rdGeneration Partnership Project 2” (3GPP2). These various radiotechnologies and standards are known in the art. For clarity, certainaspects of the techniques are described below for UMB, and UMBterminology is used in much of the description below. UMB is describedin 3GPP2 C.S0084-001, entitled “Physical Layer for Ultra MobileBroadband (UMB) Air Interface Specification,” and 3GPP2 C.S0084-002,entitled “Medium Access Control Layer For Ultra Mobile Broadband (UMB)Air Interface Specification,” both dated August 2007 and publiclyavailable.

System 100 may utilize orthogonal frequency division multiplexing (OFDM)and/or single-carrier frequency division multiplexing (SC-FDM). OFDM andSC-FDM partition the system bandwidth into multiple (K) orthogonalsubcarriers, which are also commonly referred to as tones, bins, etc.Each subcarrier may be modulated with data. In general, modulationsymbols are sent in the frequency domain with OFDM and in the timedomain with SC-FDM. The spacing between adjacent subcarriers may befixed, and the number of subcarriers may be dependent on the systembandwidth. For example, there may be 128, 256, 512, 1024 or 2048subcarriers for system bandwidth of 1.25, 2.5, 5, 10 or 20 MHz,respectively.

FIG. 2 shows a design of a superframe structure 200 that may be used forsystem 100. The transmission timeline for each link may be partitionedinto units of superframes. Each superframe may span a particular timeduration, which may be fixed or configurable. On the forward link, eachsuperframe may include a preamble followed by M physical layer (PHY)frames, where M may be any integer value. On the reverse link, eachsuperframe may include M PHY frames, where the first PHY frame may beextended by the length of the superframe preamble on the forward link.In the design shown in FIG. 2, each superframe includes 25 PHY frameswith indices of 0 through 24. Each PHY frame may carry traffic data,signaling, pilot, etc.

In one design, the superframe preamble includes eight OFDM symbols withindices of 0 through 7. OFDM symbol 0 comprises a Forward PrimaryBroadcast Control Channel (F-PBCCH) that carries information fordeployment-specific parameters. OFDM symbols 1 through 4 comprises aForward Secondary Broadcast Control Channel (F-SBCCH) that carriesinformation for sector-specific parameters as well as a Forward QuickPaging Channel (F-QPCH) that carries paging information. OFDM symbols 5,6 and 7 comprise time division multiplexed (TDM) pilots 1, 2 and 3,respectively, which may be used by terminals for initial acquisition.TDM pilot 1 is used as a Forward Acquisition Channel (F-ACQCH). AForward Other-Sector-Interference Channel (F-OSICH) is sent in TDMpilots 2 and 3. The superframe preamble may also be defined in othermanners.

The system may support hybrid automatic retransmission (HARQ). WithHARQ, one or more transmissions may be sent for a packet until thepacket is decoded correctly or is terminated by some other condition.Multiple (Q) HARQ interlaces may be defined, with HARQ interlace iincluding PHY frames i, Q+i, 2Q+i, etc., for iε{0, . . . , Q−1}. Eachpacket may be sent on one HARQ interlace, and one or more HARQtransmissions may be sent for the packet on that HARQ interlace. An HARQtransmission is a transmission for one packet in one PHY frame.

Multiple (S) subzones may be defined, with each subzone corresponding toa different portion of the system bandwidth. A subzone may also bereferred to as a subband, a frequency segment, etc. In general, asubzone may correspond to physical frequency resources (e.g.,subcarriers) or logical frequency resources (e.g., hop ports) that maybe mapped to physical frequency resources. In one design, K hop portsmay be defined and may be mapped to the K total subcarriers based on aknown mapping. The hop ports may simplify the allocation of resources.The K hop ports may be arranged into S subzones, with each subzoneincluding L hop ports, where L and S may be fixed or configurablevalues. For example, L may be equal to 64 or 128, and S may be dependenton the system bandwidth.

FIG. 2 shows a specific frame structure design. Other frame structuresmay also be used to send traffic data, signaling, pilot, etc. The systembandwidth may also be partitioned in other manners.

Each sector may receive transmissions from terminals within the sectoras well as transmissions from terminals in other sectors. The totalinterference observed by each sector is composed of (i) intra-sectorinterference from terminals within the same sector and (ii) inter-sectorinterference from terminals in other sectors. The inter-sectorinterference is also referred to as other sector interference (OSI) andmay be mitigated as described below.

In an aspect, each sector may determine and transmit OSI indicationsthat convey the amount of interference observed by that sector. An OSIindication may also be referred to as an OSI value, an OSI indicator, aninterference indicator, etc. In one design, each sector may generate andtransmit the OSI indications shown in Table 1.

TABLE 1 OSI Description Regular OSI Convey inter-sector interferenceaveraged over a Indication larger frequency range (e.g., the entiresystem bandwidth) and across a longer time interval (e.g., onesuperframe). Fast OSI Convey inter-sector interference averaged over aIndication smaller frequency range (e.g., one subzone) and across ashorter time interval (e.g., one PHY frame).

For clarity, the generation of OSI indications by one sector 112 isdescribed below. Sector 112 may estimate the interference observed bythat sector on different time frequency resources. The interference maybe quantified by an interference-over-thermal (IoT) or some otherquantity. IoT is a ratio of the total interference power observed by asector to the thermal noise power. Sector 112 may average theinterference over the entire system bandwidth and across a superframe toobtain a long-term average of the interference. In one design, sector112 may compare the long-term average interference against a set ofthresholds to determine a regular OSI indication, as follows:

$\begin{matrix}{{{Regular\_ OSI}(n)} = \left\{ \begin{matrix}{‘2’} & {{{{if}\mspace{14mu} {Th}\; 2} \leq {{Interference}_{{long} - {term}}(n)}},} \\{‘1’} & {{{{if}\mspace{14mu} {Th}\; 1} \leq {{Interference}_{{long} - {term}}(n)} < {{Th}\; 2}},} \\{‘0’} & {{{{if}\mspace{14mu} {{Interference}_{{long} - {term}}(n)}} < {{Th}\; 1}},}\end{matrix} \right.} & {{Eq}\mspace{14mu} (1)}\end{matrix}$

where Interference_(long-term)(n) is the long-term average interferencefor superframe n, Th1 and Th2 are thresholds for generating the regularOSI indication, and Regular_OSI(n) is the regular OSI indication forsuperframe n.

The Th1 threshold may be set to a target operating point for sector 112or the system. The Th2 threshold may be set to a higher value used todetect excessive interference at sector 112. In this case, the regularOSI value may be set to ‘0’ to indicate low inter-sector interference,to ‘1’ to indicate moderate inter-sector interference, and ‘2’ toindicate excessive inter-sector interference. The regular OSI indicationmay also be generated in other manners and may comprise any number ofbits of information.

Sector 112 may also average the interference over each subzone andacross a PHY frame to obtain a short-term average of the interference.In one design, sector 112 may compare the short-term averageinterference against a threshold to determine a fast OSI indication, asfollows:

$\begin{matrix}{{{Fast\_ OSI}\left( {n,m,s} \right)} = \left\{ \begin{matrix}{‘1’} & {{{{if}\mspace{14mu} {{Interference}_{{short} - {term}}\left( {n,m,s} \right)}} \geq {{Th}\; 3}},} \\{‘0’} & {{{{if}\mspace{14mu} {{Interference}_{{short} - {term}}\left( {n,m,s} \right)}} < {{Th}\; 3}},}\end{matrix} \right.} & {{Eq}\mspace{14mu} (2)}\end{matrix}$

-   where Interference_(short-term)(n,m,s) is the short-term average    interference for subzone s in PHY frame m of superframe n,    -   Th3 is a threshold for generating the fast OSI indication, and    -   Fast_OSI(n,m,s) is the fast OSI indication for subzone s in PHY        frame m of superframe n.

In the design shown in equation (2), the fast OSI indication is set to‘1’ if the short-term average interference is equal to or greater thanthe Th3 threshold and to ‘0’ otherwise. The fast OSI indication may alsobe generated in other manners and may comprise any number of bits ofinformation. The thresholds may be selected such that Th3>Th2>Th1. Inthis case, the fast OSI indication may be used to control the tail ofthe interference distribution when high interference is observed atsector 112. Sector 112 may observe different amounts of interference ondifferent subzones and/or in different PHY frames and may generatedifferent fast OSI indications for different subzones in different PHYframes.

In general, the regular and fast OSI indications may be determined basedon any interference metric and any function. A function of the measuredinterference over different time frequency resources may be used togenerate the OSI indications, as described above. In another design, afunction of the average and maximum interference measured over differenttime frequency resources may be used to generate the OSI indications.This function may be especially applicable for the fast OSI indications.

The regular OSI indication may convey the overall interference observedby sector 112 over all or a large portion of the system bandwidth andacross an extended period of time (e.g., a superframe). The regular OSIindication may be used for power control by all or many terminals inneighbor sectors. The fast OSI indications may convey the interferenceobserved by sector 112 in specific portions (e.g., subzones) of thesystem bandwidth and in specific time intervals (e.g., PHY frames). Thefast OSI indications may be used for power control by specific terminalsin neighbor sectors operating in subzones and PHY frames with highinterference.

Sector 112 may also estimate interference from terminals in specificneighbor sectors and may generate fast OSI indications for specificneighbor sectors. The terminals in each neighbor sector causing highinterference, as indicated by the fast OSI indication for that neighborsector, may reduce their transmit power to mitigate interference tosector 112.

In general, fast OSI indications may be generated for differentsubzones, different PHY frames, different neighbor sectors, etc., or anycombination thereof. Different regular and/or fast OSI indications maybe grouped together for a subzone, a subzone and sector combination,etc. For clarity, the following description is for the design in whichfast OSI indications are generated for each subzone in each PHY frame.

Sector 112 may transmit the regular OSI indication on the F-OSICH invarious manners. It may be desirable to transmit the F-OSICH over alarge coverage area so that the F-OSICH can be decoded by terminals notserved by sector 112. It may also be desirable for the F-OSICH to havethe same coverage as the TDM/acquisition pilots, which may penetrate farinto neighbor sectors. It may further be desirable for the F-OSICH to bedecodable without requiring additional information regarding thetransmitting sector (e.g., other than pilot pseudo-random (PN)information). These requirements may make the transmission of theF-OSICH expensive in terms of the required transmit power and/or timefrequency resources and may limit the rate at which the F-OSICH can besent.

In one design, the F-OSICH is sent in TDM pilots 2 and 3 in thesuperframe preamble, as shown in FIG. 2. The regular OSI indication maymodulate the phase of TDM pilots 2 and 3. In one design, the regular OSIindication may take on a value of 0, 1 or 2 and may modulate the phaseof the TDM pilots by 0, 2π/3 or 4π/3, respectively. The TDM pilots maybe sent with sufficient transmit power in order to penetrate deep intothe neighbor sectors. By embedding the F-OSICH in the TDM pilots, theregular OSI indication would have the same coverage as the TDM pilotsand may be received by terminals located throughout the neighborsectors.

Sector 112 may also transmit the fast OSI indications in variousmanners. In one design, the fast OSI indications are sent on a ForwardFast OSI Channel (F-FOSICH) in each PHY frame on the forward link.

In one design, the fast OSI indications may be sent in one or more fastOSI reports, with each report being encoded and modulated separately. Ingeneral, each report may include any number of bits for any number offast OSI indications. In one design, each report includes four bits forfour fast OSI indications, which may be for four subzones in one PHYframe. The four bits may be encoded based on a coding scheme to obtain12 code bits. The coding scheme may include a forward error detectioncode such as a cyclic redundancy check (CRC) and/or a forward errorcorrection code such as a convolutional code. In one design, a 2-bit CRCis generated for a 4-bit report, and the resultant 6 bits are encodedwith a rate 1/2 convolutional code to generate 12 code bits for thereport. The CRC and convolutional code form a rate 1/3 concatenatedcode. The 12 code bits may be mapped to 6 modulation symbols based onQPSK. The 6 modulation symbols may be sent for the report.

In general, the number of fast OSI reports to send may be dependent onvarious factors such as the system bandwidth, the number of subzones,the number of PHY frames, etc. For example, if the system bandwidth is 5MHz and four subzones of 1.25 MHz are defined, then four fast OSIindications may be generated for the four subzones in a PHY frame. Asingle report containing the four fast OSI indications may be sent with6 modulation symbols. If the system bandwidth is 20 MHz and 16 subzonesof 1.25 MHz are defined, then 16 fast OSI indications may be generatedfor the 16 subzones in a PHY frame. Four reports may be sent with atotal of 24 modulation symbols, with each report containing four fastOSI indications for four different subzones.

It is desirable to transmit the reports for the fast OSI indicationswith as little transmit power as possible. A fast OSI indication may beset to ‘1’ if the short-term average interference exceeds the Th3threshold, which may be higher than the highest threshold Th2 used forthe regular OSI indication. Thus, the likelihood of a fast OSIindication being set to ‘1’ may be low whereas the likelihood of thefast OSI indication being set to ‘0’ may be high. In one design, areport containing fast OSI indications of all zeros is transmitted withzero power by mapping this report to a sequence of modulation symbols ofzero values. For example, a 4-bit report containing ‘0000’ may beencoded and mapped to six modulation symbols of {0, 0, 0, 0, 0, 0}, witheach modulation symbol of 0 being transmitted with zero power. Ineffect, the 4-bit report of ‘0000’ is not transmitted, and no power isconsumed to convey the four fast OSI indications of all zeros. Thisdesign may reduce the amount of transmit power used to send fast OSIindications.

In another design, the fast OSI indications may be sent individually.For example, each fast OSI indication may be mapped to one or moremodulation symbols. To reduce transmit power, a fast OSI indication of‘0’ may be mapped to a modulation symbol of zero, and a fast OSIindication of ‘1’ may be mapped to a non-zero modulation symbol. Thenumber of modulation symbols to use for each fast OSI indication and/orthe transmit power for the modulation symbols may be dependent on thedesired reliability and coverage for the fast OSI indications.

In general, the fast OSI indications may be transmitted in groups and/orindividually. Transmitting the fast OSI indications in groups may allowfor more efficient encoding of a report for a group of fast OSIindications, which may allow the report to be transmitted with less timefrequency resources and/or lower transmit power for the desiredreliability and coverage. However, transmitting in groups may result inlower probability of all fast OSI indications in the report being zerosand hence not transmitted. Conversely, transmitting the fast OSIindications individually may result in higher probability ofnon-transmission of fast OSI indications with values of ‘0’, which mayreduce transmit power. However, more transmit power and/or more timefrequency resources may be used for the fast OSI indications that areactually transmitted. The manner in which the fast OSI indications aretransmitted may be selected based on a tradeoff between various factorssuch as transmit power, resource usage, coverage, reliability, etc.

On the reverse link, each terminal may be allowed to transmit at a powerlevel that is as high as possible while keeping interference to withinacceptable levels. A terminal located closer to its serving sector maybe allowed to transmit at a higher power level since this terminal willlikely cause less interference to neighbor sectors. Conversely, aterminal located farther away from its serving sector and near thecoverage edge may be allowed to transmit at a lower power level sincethis terminal may cause more interference to neighbor sectors.Controlling transmit power in this manner may reduce the interferenceobserved by each sector while allowing terminals with good channelconditions to achieve higher data rates.

A given terminal 120 x may adjust its transmit power based on a powercontrol mechanism in order to achieve both reliable transmission to itsserving sector as well as an acceptable level of interference atneighbor sectors. In general, transmit power may be given by (i) a powerspectral density (PSD) in units of decibels/Hertz (dB/Hz), (ii) transmitpower per modulation symbol, or (iii) some other metric.

In the description below, transmit power is given per modulation symbol.In one design, terminal 120 x may adjust the transmit power of areference channel to achieve a desired level of performance for thereference channel. Terminal 120 may then determine the transmit power ofa data/traffic channel based on the transmit power of the referencechannel. The reference channel may be a Reverse Pilot Channel (R-PICH),an acknowledgement channel, a dedicated control channel, an accesschannel, a request channel, etc. In one design that is described below,the reference channel is the R-PICH, and the data/traffic channel is aReverse OFDMA Data Channel (R-ODCH).

In one design, closed-loop power control may be performed for theR-PICH. For the closed-loop power control, the serving sector mayreceive the R-PICH from terminal 120 x, determine the received signalquality of the R-PICH, and send a power control (PC) bit of ‘1’ if thereceived signal quality is below a threshold or ‘0’ otherwise. Terminal120 x may receive the PC bit from the serving sector and may adjust thetransmit power of the R-PICH, as follows:

$\begin{matrix}{P_{PICH} = \left\{ \begin{matrix}{P_{PICH} + P_{STEP}} & {{{{if}\mspace{14mu} {PC}\mspace{14mu} {bit}} = {‘1’}},} \\{P_{PICH} - P_{STEP}} & {{{{if}\mspace{14mu} {PC}\mspace{14mu} {bit}} = {‘0’}},}\end{matrix} \right.} & {{Eq}\mspace{14mu} (3)}\end{matrix}$

-   where P_(STEP) is a power control step size in units of decibels    (dB), and

P_(PICH) is the transmit power of the R-PICH for each modulation symbol.

The closed-loop power control adjusts the transmit power of the R-PICHto achieve the desired received signal quality for the R-PICH. Theclosed-loop power control may also be performed for another referencechannel to achieve a target level of performance (e.g., a target errorrate) for that reference channel.

In one design, delta-based power control may be performed for theR-ODCH. For the delta-based power control, the transmit power of theR-ODCH may be set based on the transmit power of the R-PICH and a delta,which is an offset relative to the R-PICH. In one design, terminal 120 xmay maintain a single delta and may adjust this delta based on theregular and fast OSI indications received from neighbor sectors. Inanother design, terminal 120 x may maintain multiple deltas, which mayinclude (i) a slow delta that may be adjusted based on the regular OSIindication and (ii) one or more fast deltas that may be adjusted basedon the fast OSI indications. The transmit power may be determined basedon the fast and/or slow deltas.

In one design, the transmit power of the R-ODCH may be determined asfollows:

P _(ODCH,s) =P _(PICH)+Delta_(tx,j,s)+Boost,  Eq (4)

where

Delta_(tx,i,s) is a fast delta for subzone s in HARQ interlace i,

Boost is a boost in transmit power for a current HARQ transmission, and

P_(ODCH) is the transmit power of the R-ODCH for each modulation symbol.

In the design shown in equation (4), a fast delta may be maintained foreach subzone s in each HARQ interlace i of interest. Each packet may besent on the R-ODCH in a particular subzone of a particular HARQinterlace. The delta applicable for each packet may then be used todetermine the transmit power for that packet. The Boost may be a zero ornon-zero value and may be the same for all HARQ transmissions ordifferent for different HARQ transmissions. The transmit power of theR-ODCH may also be determined based on other factors such as quality ofservice (QoS), etc.

In one design, each fast delta may be updated based on the fast OSIindications for the subzone in the PHY frames for the HARQ interlace forthat fast delta, as follows:

$\begin{matrix}{{Delta}_{{tx},i,s} = \left\{ \begin{matrix}{{Delta}_{{tx},i,s} + {FastOSIStepUp}} & {{{{if}\mspace{14mu} {all}\mspace{14mu} {FastOSI}_{j,s}} = {‘0’}},} \\{{Delta}_{{tx},i,s} - {FastOSIStepDown}} & {{{{if}\mspace{14mu} {any}\mspace{14mu} {FastOSI}_{j,s}} = {‘1’}},}\end{matrix} \right.} & {{Eq}\mspace{14mu} (5)}\end{matrix}$

where

FastOSIStepUp is an up step for the fast delta,

FastOSIStepDown is a down step for the fast delta, and

FastOSI_(j,s) is the fast OSI indication from neighbor sector j forsubzone s.

Terminal 120 x may maintain a set of neighbor sectors for each subzoneof interest as described below. This set may be referred to as a monitorset. Terminal 120 x may determine the fast delta for each subzone basedon only the fast OSI indications from the neighbor sectors in themonitor set for that subzone. In one design, terminal 120 x may adjustthe fast delta only if it has used the fast delta for data transmissionin a previous HARQ interlace and in response to the corresponding fastOSI indication. In another design, terminal 120 x may adjust the fastdelta at all times, even during periods of no transmission and forunassigned HARQ interlaces. A decision to adjust the fast delta may alsobe based on buffer size, etc.

The fast delta may be constrained to be within a range of values, asfollows:

$\begin{matrix}{{Delta}_{{tx},i,s} = \left\{ \begin{matrix}{Delta}_{{{ma}\; x},i,s} & {{{{if}\mspace{14mu} {Delta}_{{tx},i,s}} > {Delta}_{{m\; {ax}},i,s}},} \\{Delta}_{{m\; i\; n},i,s} & {{{{if}\mspace{14mu} {Delta}_{{tx},i,s}} < {Delta}_{{m\; i\; n},i,s}},} \\{Delta}_{{tx},i,s} & {otherwise}\end{matrix} \right.} & {{Eq}\mspace{14mu} (6)}\end{matrix}$

where Delta_(max,i,s) is a maximum value for Delta_(tx,i,s), and

Delta_(min,i,s) is a minimum value for Delta_(tx,i,s).

The minimum and maximum values for the fast delta may be selected toachieve good performance and may be fixed or configurable values. Forexample, the minimum and maximum fast delta values may be set based onthe dynamic range of the received signal, the amount of intra-sectorinterference at the serving sector, etc.

Terminal 120 x may identify neighbor sectors to include in the monitorset for each subzone based on various metrics. In one design, terminal120 x uses a channel difference metric, which is the difference betweenthe channel gain of a neighbor sector and the channel gain of theserving sector. The channel gain of each sector may be estimated basedon the TDM pilots, other pilots, pilot quality indicator (PQI), and/orother transmissions sent on the forward link by that sector. The channeldifference for a neighbor sector may be computed as follows:

$\begin{matrix}{{{ChanDiff}_{j} = {\frac{{RxPower}_{RLSS}}{{EffectiveTxPower}_{RLSS}} \cdot \frac{{EffectiveTxPower}_{j}}{{RxPower}_{j}}}},} & {{Eq}\mspace{14mu} (7)}\end{matrix}$

where

RxPower_(RLSS) is the received power for the serving sector on thereverse link,

EffectiveTransmitPower_(RLSS) is the transmit power for the servingsector,

RxPower_(j) is the received power for neighbor sector j,

EffectiveTransmitPower_(j) is the transmit power for neighbor sector j,and

ChanDiff_(j) is the channel difference for neighbor sector j.

The channel gain for a sector is equal to the received power divided bythe transmitted power. The channel difference for neighbor sector j isequal to a ratio of the channel gain for the serving sector to thechannel gain for neighbor sector j. Terminal 120 x may add neighborsector j to the monitor set if ChanDiff_(j) is less than or equal to anadd threshold. This criterion may ensure that the received signalstrength for neighbor sector j is sufficiently strong and that the fastOSI indications from sector j can be reliably received. Terminal 120 xmay likely cause significant interference to only the neighbor sectorsin the monitor set and may thus adjust the fast delta based on only thefast OSI indications from these sectors.

Terminal 120 x may update a slow delta based on various factors such asthe regular OSI indications received from neighbor sectors in a monitorset, the channel differences for the neighbor sectors, the currenttransmit power or PSD, etc. Terminal 120 x may determine a decisionvariable for each neighbor sector based on pertinent factors for thatsector. The decision variable may indicate whether or not to adjust theslow delta and/or how much to adjust the slow delta. Terminal 120 x maycompute a weighted decision for all neighbor sectors in the monitor setbased on the decision variables and the channel differences for thesesectors. Terminal 120 x may then adjust the slow delta based on theweighted decision. The slow delta may be sent back to the serving sectorand may be used along with other information by the serving sector todetermine C/I values for new assignments for terminal 120 x.

In general, terminal 120 x may adjust the slow and fast deltas based onthe same or different sets of parameters and with the same or differentalgorithms. Parameters that may be different for slow and fast deltaadjustments may include up and down step sizes, decision thresholds,etc.

The initial values of the fast and slow deltas may be determined invarious manners. In one design, an initial delta value may be computedsuch that:

$\begin{matrix}{{\frac{{averageIoT} + {{pCoT}*{Delta}}}{averageIoT} < {maxIoTRise}},} & {{Eq}\mspace{14mu} (8)}\end{matrix}$

where

-   -   averageIoT is an average interference-over-thermal (IoT) at a        neighbor sector,    -   pCoT is a received carrier-power-over-thermal (CoT) for the        reference channel as measured at the neighbor sector, and    -   maxIoTRise is a maximum allowable rise in IoT at the neighbor        sector.

If the initial delta value from equation (8) is smaller than a minimumdelta value, Delta_(min), then the maximum supportable bandwidth,W_(max), may be reduced such that:

$\begin{matrix}{{\frac{{averageIoT} + {\left( {W_{m\; {ax}}/W_{total}} \right)*{pCoT}*{Delta}_{m\; i\; n}}}{averageIoT} < {maxIoTRise}},} & {{Eq}\mspace{14mu} (9)}\end{matrix}$

where W_(total) is the total system bandwidth. The maximum supportablebandwidth may be sent to the serving sector and used to assign bandwidthto terminal 120 x.

If terminal 120 x is assigned a particular bandwidth, W, then theinitial delta value may be computed such that:

$\begin{matrix}{\frac{{averageIoT} + {\left( {W/W_{total}} \right)*{pCoT}*{Delta}}}{averageIoT} < {{maxIoTRise}.}} & {{Eq}\mspace{14mu} (10)}\end{matrix}$

The amount of interference at the beginning of each transmission burstmay be controlled by limiting the initial maximum supportable bandwidthW_(max) based on the current delta value. This W_(max) may be computedusing equation (10), with W representing W_(max). Terminal 120 x maysend W_(max) to the serving sector, which may gradually increase thebandwidth over subsequent assignments to allow enough time for the fastOSI indications to adjust the delta value.

The initial delta value may also be determined in other manners and maybe referred to as open loop adjustments. In one design, terminal 120 xmay make open loop adjustments only at the beginning of eachtransmission burst. In another design, if terminal 120 x is notscheduled on some HARQ interlaces, then terminal 120 x may use theinitial delta value as a maximum value for the fast delta in order toprevent the fast delta from becoming too large due to little OSIindication activity.

FIG. 3 shows a design of a power control mechanism 300 that may be usedfor the reverse link. Terminal 120 x may communicate with serving sector110 and may cause interference to neighbor sectors. Power controlmechanism 300 includes a reference loop 302 and an outer loop 304.Reference loop 302 operates between terminal 120 x and serving sector110 and adjusts the transmit power of the R-PICH. Outer loop 304operates between terminal 120 x and the neighbor sectors and adjusts theslow and fast delta based on the regular and fast OSI indicationsreceived from the neighbor sectors. Reference loop 302 and outer loop304 may operate concurrently but may be updated at different rates,e.g., reference loop 302 may be updated more frequently than outer loop304.

For reference loop 302, a unit 310 at serving sector 110 may estimatethe received signal quality of the R-PICH from terminal 120 x. A unit312 may compare the received signal quality against a target value andmay generate PC bits based on the comparison results. A transmitprocessor 314 may process and transmit the PC bits as well as pilot,traffic data, and signaling on the forward link (cloud 352). Terminal120 x may receive the PC bits from sector 110. A PC bit processor 360may detect each received PC bit and provide a corresponding detected PCbit. A unit 362 may adjust the transmit power of the R-PICH based on thedetected PC bits from processor 360, e.g., as shown in equation (3).

For outer loop 304, neighbor sectors 112 and 114 may receivetransmissions on the reverse link. At each neighbor sector, a unit 320may estimate the inter-sector interference observed by that sector fromterminals in other sectors. A unit 322 may generate regular and fast OSIindications based on the estimated interference, e.g., as shown inequations (1) and (2). A transmit processor 324 may process and transmitthe regular and fast OSI indications on the forward link to theterminals in the other sectors. Processor 324 may also process andtransmit pilot, traffic data, and signaling. Each neighbor sector mayalso forward the OSI indications to nearby sectors for transmission tothe terminals in the nearby sectors. At terminal 120 x, an OSI processor380 may receive the regular and fast OSI indications from the neighborsectors and provide detected OSI values. A channel estimator 382 maydetermine the channel difference for each neighbor sector based on pilotand/or other transmissions. A unit 384 may adjust the slow and fastdeltas based on the detected OSI values, the channel differences, andother parameters. A unit 386 may determine the transmit power of theR-ODCH based on the transmit power of the R-PICH, the deltas, and/orother parameters, e.g., as shown in equation (4). A transmit processor364 may use the transmit power of the R-ODCH for data transmission toserving sector 110.

For clarity, delta-based power control using the fast delta adjustedbased on the fast OSI indications has been described above. The transmitpower of terminal 120 x may also be adjusted with the regular and fastOSI indications based on other power control algorithms.

FIG. 4 shows a design of a process 400 for transmitting OSI indications.Process 400 may be performed by a sector/base station. Multiple OSIindications for multiple subzones may be determined, e.g., in eachframe, with each subzone corresponding to a different portion of thesystem bandwidth (block 412). These OSI indications may correspond tothe fast OSI indications described above. For block 412, theinterference observed by the sector due to terminals in neighbor sectorsmay be estimated. The estimated interference may be averaged over eachsubzone to obtain an average interference for that subzone. The OSIindication for each subzone may be determined based on the averageinterference for that subzone. Each OSI indication may comprise a singlebit that may be set (i) to a first value (e.g., ‘1’) if highinterference is observed in a corresponding subzone or (ii) to a secondvalue (e.g., ‘0’) if high interference is not observed in thecorresponding subzone.

The multiple OSI indications may be processed for transmission, e.g.,broadcast to terminals in neighbor sectors (block 414). For block 414,at least one report may be generated for the multiple OSI indications,with each report including at least one OSI indication for at least onesubzone (block 416). For example, each report may include four OSIindications for four subzones. Each report may include four bits for thefour OSI indications and may be encoded to obtain code bits, which maybe mapped to a sequence of six modulation symbols (block 418). Asequence of six modulation symbols of zero values may be generated foreach report with all four OSI indications set to zero to indicate lackof high interference in the four corresponding subzones.

A regular OSI indication for the system bandwidth may be determined,e.g., in each superframe based on a long-term average interference overthe system bandwidth and across the superframe (block 420). The regularOSI indication may be determined based on at least one first thresholdfor comparing the long-term average interference. The multiple OSIindications may be determined based on at least one second thresholdthat is higher than the at least one first threshold. This may result inthe multiple OSI indications being less likely to be set than theregular OSI indication. The multiple OSI indication may be transmittedat a first rate (e.g., each frame) and over a first coverage area (block422). The regular OSI indication may be transmitted at a second rate(e.g., each superframe) that may be slower than the first rate and overa second coverage area, which may be wider than the first coverage area(block 424).

FIG. 5 shows a design of an apparatus 500 for transmitting OSIindications. Apparatus 500 includes means for determining multiple OSIindications for multiple subzones (module 512), means for processing themultiple OSI indications for transmission (module 514), means forgenerating at least one report for the multiple OSI indications (module516), means for encoding and symbol mapping each report to a sequence ofmodulation symbols (module 518), means for determining a regular OSIindication for the system bandwidth (module 520), means for transmittingthe multiple OSI indication (module 522), and means for transmitting theregular OSI indication (module 524).

FIG. 6 shows a design of a process 600 for receiving OSI indications.Process 600 may be performed by a terminal. At least one OSI indicationfor at least one subzone may be received, with each subzonecorresponding to a different portion of the system bandwidth (block612). The at least one OSI indication may be received from at least oneneighbor sector in a monitor set. The monitor set may be updated basedon channel gains for neighbor sectors and channel gain for a servingsector.

Transmit power (e.g., for a data channel) may be determined based on theat least one OSI indication (block 614). For block 614, at least onedelta for the at least one subzone may be adjusted based on the at leastone OSI indication (block 616). The delta for each subzone may be (i)increased if all OSI indications for the subzone indicate lack of highinterference or (ii) decreased if any OSI indication for the subzoneindicates high interference. The transmit power for a reference channelmay be determined based on closed-loop power control (block 618). Thetransmit power for each subzone may then be determined based on a deltafor that subzone and the transmit power for the reference channel (block620).

The at least one OSI indication for the at least one subzone may bereceived for at least one interlace (e.g., HARQ interlace), with eachinterlace including frames spaced apart by a predetermined number offrames. A delta for each subzone in each interlace may be adjusted basedon OSI indications received for the subzone in the interlace and may beused to determine the transmit power for the subzone in the interlace.

A regular OSI indication for the system bandwidth may also be receivedin each superframe. The transmit power may be determined based furtheron the regular OSI indication.

FIG. 7 shows a design of an apparatus 700 for receiving OSI indications.Apparatus 700 includes means for receiving at least one OSI indicationfor at least one subzone (module 712), means for determining transmitpower based on the at least one OSI indication (module 714), means foradjusting at least one delta for the at least one subzone based on theat least one OSI indication (module 716), means for determining thetransmit power for a reference channel based on closed-loop powercontrol (module 718), and means for determining the transmit power foreach subzone based on a delta for that subzone and the transmit powerfor the reference channel (module 720).

The modules in FIGS. 5 and 7 may comprise processors, electronicsdevices, hardware devices, electronics components, logical circuits,memories, etc., or any combination thereof.

FIG. 8 shows a block diagram of a design of terminal 120 x, servingsector/base station 110, and neighbor sector/base station 112 in FIG. 1.At sector 110, a transmit processor 814 a may receive traffic data froma data source 812 a, signaling (e.g., PC bits) from acontroller/processor 830 a, and/or assignments of time frequencyresources from scheduler 834 a. Transmit processor 814 a may process(e.g., encode, interleave, and symbol map) the traffic data, signaling,and pilot and provide modulation symbols. A modulator (MOD) 816 a mayperform modulation on the modulation symbols (e.g., for OFDM) andprovide output chips. A transmitter (TMTR) 818 a may conditions (e.g.,convert to analog, amplify, filter, and upconvert) the output chips andgenerate a forward link signal, which may be transmitted via an antenna820 a.

Sector 112 may similarly process traffic data and signaling forterminals served by sector 112. The traffic data, signaling, and pilotmay be processed by a transmit processor 814 b, modulated by a modulator816 b, conditioned by a transmitter 818 b, and transmitted via anantenna 820 b.

At terminal 120 x, an antenna 852 may receive the forward link signalsfrom sectors 110 and 112 and possibly other sectors. A receiver (RCVR)854 may condition (e.g., filter, amplify, downconvert, and digitize) areceived signal from antenna 852 and provide samples. A demodulator(DEMOD) 856 may perform demodulation on the samples (e.g., for OFDM) andprovide symbol estimates. A receive processor 858 may process (e.g.,symbol demap, deinterleave, and decode) the symbol estimates, providedecoded data to a data sink 860, and provide decoded signaling (e.g., PCbits, OSI indications, etc.) to a controller/processor 870.

On the reverse link, a transmit processor 882 may receive and processtraffic data from a data source 880 and signaling fromcontroller/processor 870 and provide symbols. A modulator 884 mayperform modulation on the symbols (e.g., for OFDM, CDM, etc.) andprovide output chips. A transmitter 886 may condition the output chipsand generate a reverse link signal, which may be transmitted via antenna852.

At each sector, the reverse link signals from terminal 120 x and otherterminals may be received by antenna 820, conditioned by a receiver 840,demodulated by a demodulator 842, and processed by a receive processor844. Processor 844 may provide decoded data to a data sink 846 anddecoded signaling to controller/processor 830. At serving sector 110,demodulator 842 a may estimate the received signal quality for terminal120 x. Controller/processor 830 a may generate PC bits for terminal 120x based on the received signal quality. At neighbor sector 112,demodulator 842 b may estimate the interference observed by the sector.Controller/processor 830 b may generate the regular and fast OSIindications based on the estimated interference.

Controllers/processors 830 a, 830 b and 870 may direct the operation atsectors 110 and 112 and terminal 120 x, respectively. Memories 832 a,832 b and 872 may store data and program codes for sectors 110 and 112and terminal 120 x, respectively. Schedulers 834 a and 834 b mayschedule terminals communicating with sectors 110 and 112, respectively,and may assign channels and/or time frequency resources to theterminals.

The processors in FIG. 8 may perform various functions for thetechniques described herein. For example, processor 830 a may implementunits 310 and/or 312 in FIG. 3 for serving sector 110. Processor 830 bmay implement units 320 and/or 322 in FIG. 3 for neighbor sector 112 andmay perform process 400 in FIG. 4 and/or other processes for thetechniques described herein. Processor 858, 870 and/or 882 may implementsome or all of units 360 through 386 in FIG. 3 for terminal 120 x andmay perform process 600 in FIG. 6 and/or other processes for thetechniques described herein.

The concept of channels described herein may refer to information ortransmission types that may be transmitted by a terminal or a basestation. It does not require or utilize fixed or predetermined sets ofsubcarriers, time periods, or other resources dedicated to suchtransmissions. Furthermore, time frequency resources are exemplaryresources that may be assigned and/or used for sending data andmessages/signaling. The time frequency resources may also comprisefrequency subcarriers, transmission symbols, and/or other resources inaddition to time frequency resources.

The techniques described herein may be implemented by various means. Forexample, these techniques may be implemented in hardware, firmware,software, or a combination thereof. For a hardware implementation, theprocessing units used to perform the techniques at an entity (e.g., abase station or a terminal) may be implemented within one or moreapplication specific integrated circuits (ASICs), digital signalprocessors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs), field programmable gate arrays(FPGAs), processors, controllers, micro-controllers, microprocessors,electronic devices, other electronic units designed to perform thefunctions described herein, a computer, or a combination thereof.

For a firmware and/or software implementation, the techniques may beimplemented with code (e.g., procedures, functions, modules,instructions, etc.) that performs the functions described herein. Ingeneral, any computer/processor-readable medium tangibly embodyingfirmware and/or software code may be used in implementing the techniquesdescribed herein. For example, the firmware and/or software code may bestored in a memory (e.g., memory 832 a, 832 b or 872 in FIG. 8) andexecuted by a processor (e.g., processor 830 a, 830 b or 870). Thememory may be implemented within the processor or external to theprocessor. The firmware and/or software code may also be stored in acomputer/processor-readable medium such as random access memory (RAM),read-only memory (ROM), non-volatile random access memory (NVRAM),programmable read-only memory (PROM), electrically erasable PROM(EEPROM), FLASH memory, floppy disk, compact disc (CD), digitalversatile disc (DVD), magnetic or optical data storage device, etc. Thecode may be executable by one or more computers/processors and may causethe computer/processor(s) to perform certain aspects of thefunctionality described herein.

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Thus, the disclosure is not intended to be limited tothe examples and designs described herein but is to be accorded thewidest scope consistent with the principles and novel features disclosedherein.

What is claimed is:
 1. An apparatus for wireless communication,comprising: at least one processor configured to determine multipleother sector interference (OSI) indications for multiple subzones, eachsubzone corresponding to a different portion of system bandwidth, and toprocess the multiple OSI indications for transmission; and a memorycoupled to the at least one processor.
 2. The apparatus of claim 1,wherein the at least one processor is configured to determine themultiple OSI indications for the multiple subzones in each frame of apredetermined duration.
 3. The apparatus of claim 1, wherein the atleast one processor is configured to estimate interference observed by asector due to terminals in neighbor sectors, and to determine themultiple OSI indications for the multiple subzones based on theestimated interference.
 4. The apparatus of claim 3, wherein the atleast one processor is configured to average the estimated interferenceover each subzone to obtain an average interference for the subzone, andto determine an OSI indication for each subzone based on the averageinterference for the subzone.
 5. The apparatus of claim 1, wherein eachOSI indication comprises a single bit, and wherein the at least oneprocessor is configured to set the single bit for each OSI indication toa first value if high interference is observed in a correspondingsubzone, and to set the single bit for each OSI indication to a secondvalue if high interference is not observed in the corresponding subzone.6. The apparatus of claim 3, wherein the at least one processor isconfigured to average the estimated interference over the systembandwidth to obtain a long-term average interference, and to determine aregular OSI indication based on the long-term average interference. 7.The apparatus of claim 1, wherein the at least one processor isconfigured to generate at least one report for the multiple OSIindications, each report comprising at least one OSI indication for atleast one subzone.
 8. The apparatus of claim 7, wherein each reportcomprises four OSI indications for four subzones.
 9. The apparatus ofclaim 8, wherein each report comprises four bits for the four OSIindications, and wherein the at least one processor is configured toencode each report of four bits to obtain code bits, and to generate asequence of six modulation symbols for each report based on the codebits for the report.
 10. The apparatus of claim 7, wherein the at leastone processor is configured to generate a sequence of modulation symbolsof zero values for each report with all of the at least one OSIindication set to a predetermined value.
 11. The apparatus of claim 8,wherein the at least one processor is configured to generate a sequenceof six modulation symbols of zero values for each report with all fourOSI indications set to zero to indicate lack of high interference in thefour corresponding subzones.
 12. The apparatus of claim 1, wherein theat least one processor is configured to broadcast the multiple OSIindications to terminals in neighbor sectors.
 13. The apparatus of claim1, wherein the at least one processor is configured to determine aregular OSI indication for the system bandwidth.
 14. The apparatus ofclaim 13, wherein the at least one processor is configured to transmitthe multiple OSI indication for the multiple subzones at a first rate,and to transmit the regular OSI indication for the system bandwidth at asecond rate slower than the first rate.
 15. The apparatus of claim 13,wherein the at least one processor is configured to transmit themultiple OSI indication for the multiple subzones over a first coveragearea, and to transmit the regular OSI indication for the systembandwidth over a second coverage area wider than the first coveragearea.
 16. The apparatus of claim 13, wherein the at least one processoris configured to determine the regular OSI indication based on at leastone first threshold for comparing estimated interference, and todetermine the multiple OSI indications based on at least one secondthreshold higher than the at least one first threshold.
 17. A method forwireless communication, comprising: determining multiple other sectorinterference (OSI) indications for multiple subzones, each subzonecorresponding to a different portion of system bandwidth; and processingthe multiple OSI indications for transmission.
 18. The method of claim17, wherein the determining the multiple OSI indications comprisesdetermining the multiple OSI indications for the multiple subzones ineach frame of a predetermined duration.
 19. The method of claim 17,wherein the processing the multiple OSI indications comprises generatingat least one report for the multiple OSI indications, each reportcomprising at least one OSI indication for at least one subzone.
 20. Themethod of claim 19, wherein each report comprises four OSI indicationsfor four subzones, and wherein the processing the multiple OSIindications further comprises encoding each report to obtain code bits,and generating a sequence of six modulation symbols for each reportbased on the code bits for the report.
 21. The method of claim 20,wherein the processing the multiple OSI indications further comprisesgenerating a sequence of six modulation symbols of zero values for eachreport with all four OSI indications set to zero to indicate lack ofhigh interference in the four corresponding subzones.
 22. An apparatusfor wireless communication, comprising: means for determining multipleother sector interference (OSI) indications for multiple subzones, eachsubzone corresponding to a different portion of system bandwidth; andmeans for processing the multiple OSI indications for transmission. 23.The apparatus of claim 22, wherein the means for determining themultiple OSI indications comprises means for determining the multipleOSI indications for the multiple subzones in each frame of apredetermined duration.
 24. The apparatus of claim 22, wherein the meansfor processing the multiple OSI indications comprises means forgenerating at least one report for the multiple OSI indications, eachreport comprising at least one OSI indication for at least one subzone.25. The apparatus of claim 24, wherein each report comprises four OSIindications for four subzones, and wherein the means for processing themultiple OSI indications further comprises means for encoding eachreport to obtain code bits, and means for generating a sequence of sixmodulation symbols for each report based on the code bits for thereport.
 26. The apparatus of claim 25, wherein the means for processingthe multiple OSI indications further comprises means for generating asequence of six modulation symbols of zero values for each report withall four OSI indications set to zero to indicate lack of highinterference in the four corresponding subzones.
 27. A computer programproduct, comprising: a computer-readable medium comprising: code forcausing at least one computer to determine multiple other sectorinterference (OSI) indications for multiple subzones, each subzonecorresponding to a different portion of system bandwidth; and code forcausing the at least one computer to process the multiple OSIindications for transmission.